1. Field of the Invention
The present invention relates to an electric motor and a method and an apparatus for manufacturing such a motor.
2. Description of the Related Art
Usually, a motor has a stator that includes a plurality of permanent magnets circumferentially disposed on the inside surface thereof to provide magnetic poles and a rotor that is disposed in the space surrounded by the magnetic poles. For example, JP-A-10-145990 discloses a motor in which the rotor is constituted of a center core, a plurality of coil cores on which concentrated coils or solenoid coils are mounted. The center core is disposed to be coaxial with the rotating axis of the rotor, and the coil cores are disposed around the center core. Each of the concentrated coils is wound around an insulator. Thus, a high space factor, which is a ratio of the conductor's volume to the motor's total volume, can be provided.
In the disclosed motor, the center core and the coil cores are fixed by means of concavity-convexity connection. In other words, projections are formed in one of the center core and the coil cores, and recesses are formed in the other so that the projections can be fitted into the recesses in the radial direction when they are assembled.
However, it is difficult to insert a plurality of projections into the recesses at one time, and each coil core has to be fixed to the center core.